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CVE PROGRAM SOURCE RECORDUnscored

CVE-2026-98215

selinux: preserve user SID across nested backing files

Read JSON ↗CVE.org ↗
Status
Published
Published
Updated
Assigning organization
Linux

Description

In the Linux kernel, the following vulnerability has been resolved: selinux: preserve user SID across nested backing files SELinux saves the user file SID in a backing-file security blob so it remains available after mmap() replaces vma->vm_file with a backing file. For nested backing files (overlayfs over overlayfs, or FUSE passthrough backed by overlayfs), user_file may itself be a backing file. Its fsec->sid is the SID of the mounter that opened it, rather than the user that opened the top-level file. mprotect() then checks fd { use } against the mounter SID. This can incorrectly deny access without a domain transition, or check the wrong target SID after one. Copy the saved user SID when user_file is a backing file. Keep using the regular file SID for the first backing layer. With two nested overlayfs mounts and SELinux enforcing, mprotect(PROT_READ) returns EACCES with an fd { use } denial against the mounter SID. With this change, mprotect() succeeds. Tested on arm64 QEMU with a small BusyBox initramfs and a purpose-built SELinux policy. The original test was also repeated with Fedora Cloud Base 44 userspace and gave the same result.

Affected products

Version statuses are supplied by the assigning organization. Consult the original record for detailed ranges and platform conditions.

Linux Linux

Default version status: unaffected

  • bc6c380c1159de52a252ed11f19a42c47f60a735 to < caa1b913d90d5dc07073733326d2af0f0288f089affected
  • 8bacd09f12c27710228562e4d13163e58c5f4a45 to < 6aaeec59aadcd1eafc18b049f1b759fb6b9d9569affected
  • d844702198395d3f80222777030f69db6be6b709 to < 9d99b770e7b67b00bdef9005b928aad13e1d679baffected
  • 82544d36b1729153c8aeb179e84750f0c085d3b1 to < ff20d16b2e8230c034e21540043df47222dcc09baffected
  • 82544d36b1729153c8aeb179e84750f0c085d3b1 to < 8c0c602202b9a4909b00bc3354e3c0355bc69e65affected
  • cd0e707a927a70cdfd8bc5a512a9719a87f5ed51affected
  • 6.6.144 to < 6.6.158affected
  • 6.12.95 to < 6.12.112affected
  • 6.18.38 to < 6.18.54affected
  • 7.0.4 to < 7.1affected

Linux Linux

Default version status: affected

  • 7.1affected
  • 0 to < 7.1unaffected
  • 6.6.158 to ≤ 6.6.*unaffected
  • 6.12.112 to ≤ 6.12.*unaffected
  • 6.18.54 to ≤ 6.18.*unaffected
  • 7.2.8 to ≤ 7.2.*unaffected
  • 7.3 to ≤ *unaffected

References